This invention relates to a drive system capable of providing various drive ratios and to a bicycle employing such a drive system.
Multi-speed bicycles are well known and have been in use for a number of years. One common type of multi-speed bicycle employs a derailer system used in conjunction with a number of sprockets to provide a number of "speeds" or drive ratios. Typically, for example, in a known ten speed bicycle, there are two sprockets of different sizes for a chain drive mounted on the pedal drive axle and five sprockets of varying size mounted on the axle for the rear wheel. The derailer permits the drive chain of the bicycle to be moved from one sprocket to another either at the location of the pedal drive or at the axle for the rear wheel.
Although the known drive systems for a multi-speed bicycle work reasonably well, there are several known and apparent difficulties with them. Firstly, they require the use of a number of metal sprockets and a metal drive chain and these require the use of messy lubricants which are prone to collect dirt. The known mechanism can cause damage to clothing which can get caught in the mechanism. The mechanism employs a multiplicity of moving and sometimes delicate parts which can break or stretch or fail from time to time. This mechanism is not aerodynamic which can be important in some bicycles, particularly those designed for racing. Because the various parts are made of metal, they can be relatively expensive to manufacture and the parts are subject to rust or oxidation. The known multi-speed drive system also generally requires that a standard spoked bicycle wheel, including tube and tire, be used.
Drive systems which employ V-shaped belts are also known for a variety of applications but, as far as the applicant is aware, such drive systems have never been employed to provide a multi-speed or variable speed drive suitable for a bicycle. One advantage of these drive systems is that they employ a reinforced rubber or synthetic rubber belt which can be manufactured at a reasonable cost and which does not require the use of greasy and messy lubricants.
It would be advantageous to provide a variable speed drive suitable for a bicycle that is relatively simple in its construction and that can be manufactured at a lower cost than the existing known multi-speed drive systems. Preferably, such a drive system would be made with parts or components that would be primarily or substantially non-metallic and that would employ materials such as inexpensive plastics, composites or ceramics. Drive system components made of plastics or ceramics are non-corroding, non-rusting, and easier to recycle.
It is an object of the present invention to provide a new and relatively inexpensive drive system capable of providing various drive ratios and employing a continuous V-shaped drive belt in combination with first and second pairs of members that engage this drive belt and that are conical on one side.
It is a further object of the present invention to provide a relatively inexpensive drive system capable of providing various drive ratios wherein major components thereof can be made of inexpensive non-metallic materials such as plastics. In at least one form thereof, the drive system is suitable for use on a bicycle.